Is diabetes a coronary risk equivalent? Systematic review and meta-analysis

To determine whether patients with diabetes without prior myocardial infarction (MI) have the same risk of total coronary heart disease (CHD) events as non-diabetic patients with previous myocardial infarction.

Using MEDLINE, EMBASE, Cochrane and MeSH in this systematic review and meta-analysis, extensive searching was carried out by cross-referencing from original articles and reviews. The study consisted of cohort or observational studies with hard clinical endpoints, including total CHD events (fatal or non-fatal myocardial infarction), stratified for patients with diabetes but no previous myocardial infarction, and patients without diabetes but with previous myocardial infarction. Studies with less than 100 subjects, follow-up of less than 4 years and/or without provisions for calculating CHD event rates were excluded. The review of articles and data extraction was performed by two independent authors, with any disagreements resolved by consensus.

Thirteen studies were included involving 45,108 patients. The duration of follow-up was 5-25 years (mean 13.4 years) and the age range was 25-84 years. Patients with diabetes without prior myocardial infarction have a 43% lower risk of developing total CHD events compared with patients without diabetes with previous myocardial infarction (summary odds ratio 0.56, 95% confidence interval 0.53-0.60).

This meta-analysis did not support the hypothesis that diabetes is a 'coronary heart disease equivalent'. Public health decisions to initiate cardio-protective drugs in patients with diabetes for primary CHD prevention should therefore be based on appropriate patients' CHD risk estimates rather than a 'blanket' approach of treatment.